/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.db.mpp.transformation.dag.column;

import org.apache.iotdb.tsfile.read.common.block.column.Column;

import static com.google.common.base.Preconditions.checkArgument;

public class ColumnCache {

    private int referenceCount;
    private Column column;

    public ColumnCache() {
    }

    public Column getColumn() {
        referenceCount--;
        checkArgument(referenceCount >= 0, "Exceed max call times of getColumn");
        Column res = this.column;
        // set column to null for memory control
        if (referenceCount == 0) {
            this.column = null;
        }
        return res;
    }

    public int getPositionCount() {
        return column != null ? column.getPositionCount() : 0;
    }

    public void cacheColumn(Column column, int referenceCount) {
        this.referenceCount = referenceCount;
        this.column = column;
    }

    public boolean hasCached() {
        return column != null;
    }
}
